Node system, server apparatus, scaling control method, and program

ABSTRACT

A system includes an active system that executes processing, a standby system that is able to perform at least one of scale-up and scale-down, and a control apparatus that controls system switching to set the standby system undergoing the scaled up or scaled down as a new active system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No.PCT/JP2016/052803, filed on Jan. 29, 2016, which claims the benefit ofthe priority of Japanese patent application No. 2015-017718 filed onJan. 30, 2015, the disclosure of which is incorporated herein in itsentirety by reference thereto.

TECHNICAL FIELD

The present invention relates to a node system constituting a network,server apparatus, scaling control method, and program.

BACKGROUND ART

In order to improve reliability, such a system is used in which aplurality of servers are combined to provide a redundant configuration(for instance, reference may be done to Patent Literature 1). Forexample, a duplex system comprises two servers having the sameconfiguration, and, when one active (active) server (also termed as“operation system” server or “working system” server) fails, the systemswitches to and operates with a normal server apparatus (also termed asstandby server (also termed as “waiting system” server or “reservesystem” server)).

(N+1) redundancy system is a system wherein one server apparatus isarranged as a common reserve apparatus (standby server) for N number ofserver apparatuses (active servers).

In a hot standby system, for instance, data is synchronized between anactive server and a standby server such that the standby server can takeover service (processing) in an instant, when the active system serverfails.

In a so-called cold standby system, a standby server stands by in astopped state, and when an active server fails, the standby server isstarted up to switch over the operation and processing. The cold standbysystem, in which starting up and preparation of the standby server areexecuted after the active system server fails, has limitation in termsof system downtime and service continuation.

In a system called a warm standby (Warm Standby) system, when an activeserver operates, a standby server stands with power set on and with OS(Operating System) booted up (with database content being copiedasynchronously), and, when the active system server fails, with networkswitching or the like, a user program such as a business application isinvoked, and processing is transferred to the standby server.

Patent Literature 2 discloses the following server system. Out ofservers each operating as an active system, a server in which a softwarefor update is stored, transmits the software for update other server andinstructs all servers each operating as a standby system to update tothe software for update. When the update instruction is issued, theservers each operating as a standby system update software running onthese servers to the software for update. After all the servers eachoperating as a standby system complete the update, the server in whichthe software for update is stored, switches active systems and standbysystems of all of the set of servers.

Patent Literature 3 discloses the following system. The system comprisesfirst and second databases operating on virtual machine with differentperformances, and exchanges virtual machines used by the system inresponse to an external instruction to perform scale up or scale downthe performance of the system. At this time, the system performs datasynchronization of the databases using a stream type replicationfunction provided in each of the databases. After establishment of thedata synchronization, the virtual machine that forwards an SQL(Structured Query Language) command is switched to another virtualmachine. This configuration dynamically and inexpensively achieves thescale-up/down of a database equipped with a stream type replicationfunction by utilizing the stream type replication function withoutstopping a Web service.

As a technology of virtualizing network functions, in addition tovirtualization computing and storage of a server, NFV (Network FunctionsVirtualization) and so forth that realizes network functions by means ofsoftware using an application or the like running on a virtual machine(VM) implemented on a virtualization layer such as a hypervisor on aserver is known. NFV is realized by a virtualization technology on ageneral-purpose server, as opposed to dedicated appliance (e.g., LTE(Long Term Evolution) mobile network node (e.g., MME (MobilityManagement Entity), P-GW (Packet data network Gateway), S-GW (ServingGateway), etc.)), and the functions can be changed by means of softwareat any time (e.g., refer to Non-Patent Literature 1).

[Patent Literature 1]

-   Japanese Patent No. 4479930B    [Patent Literature 2]-   Japanese Patent No. 5011655B    [Patent Literature 3]-   Japanese Patent Kokai Publication No. JP-P2012-215937A    [Non-Patent Literature 1]-   ETSI GS NFV 002 V1.2.1 (2014-12), Network Functions Virtualisation    (NFV); Architectural Framework, pp. 13-18, searched on Dec. 25,    2014, the Internet <URL:    http://www.etsi.org/deliver/etsi_gs/NFV/001_099/002/01.02.01_60/gs_NFV002v010201p.pdf>

SUMMARY

Analysis of the related technologies are given below.

A technology that dynamically scales up (increasing processingperformance) by increasing the number of virtual machines (VM) or scalesdown (decreasing processing performance) by decreasing the number ofvirtual machines (VM) according to the processing load of an applicationis known (e.g., Patent Literature 3). Patent Literature 3 discloses atechnology for suppressing data transfer amount and an increase in costspent in replacing a database when processing performance is changedaccording to load of the database. This technology dynamically achievesscales up/down without stopping a web application using a proxy thatrelays an SQL inquiry for an RDBMS (Relational Database ManagementSystem) having a stream type replication function and operating on avirtual machine instance provided by an IaaS (infrastructure as aService).

The technology disclosed in Patent Literature 3, however, cannoteffectively utilize resources due to the processing ofincreasing/decreasing VMs and a delay required for process allocationand taking over when the system is scaled up/down byincreasing/decreasing VMs according to the processing load, and also hasa problem of a process failure in a scale-down situation (findings bythe present inventors).

A main object of the present invention, invented in consideration of theproblems above, is to provide a system, apparatus, method, and recordingmedium storing a program each capable of reducing a processing delay inat least one of scale-up and/or scale-down.

According to an aspect of the present invention, there is provided asystem comprising: an active system that executes processing; a standbysystem that is able to perform at least one of scale up and scale down;and control apparatus that controls system switching to switch thestandby system undergoing the scale up or scale down to a new activesystem.

According to another aspect of the present invention, there is provideda server apparatus comprising: at least a standby system of a systemthat comprises an active system and the standby system, and

an apparatus that performs scale up or scale down of the standby systemin advance, and that switches the standby system to a new active system.

According to yet another aspect of the present invention, there isprovided a server apparatus including at least a standby system of aredundant system constituted by an active system and the standby system,the server apparatus comprises a unit that switches the standby systemto a new active system, after scaling (scaling up or scaling down) thestandby system in advance.

According to another aspect of the present invention, there is provideda scaling control method comprising:

when performing scale up or scale down of an active system, switching,to a new active system, a scaled up or scaled down standby systemprovided as a switching target of an active system executing processing.

According to yet another aspect of the present invention, there isprovided a computer-readable recording medium storing therein a programcausing a computer to execute processing comprising:

when performing of scale up or scale down of the active system,switching a scaled up or scaled down standby system provided as aswitching target of an active system executing processing to a newactive system. According to the present invention, the computer-readablerecording medium may be a non-transitory computer-readable recordingmedium (semiconductor memory or storage medium such as magnetic/opticalrecording medium) storing the program.

According to the present invention, a system, apparatus, method, andprogram capable of reducing a processing delay at the time of scaling(scale-up and/or scale-down) can be provided. Still other features andadvantages of the present invention will become readily apparent tothose skilled in this art from the following detailed description inconjunction with the accompanying drawings wherein only exemplaryembodiments of the invention are shown and described, simply by way ofillustration of the best mode contemplated of carrying out thisinvention. As will be realized, the invention is capable of other anddifferent embodiments, and its several details are capable ofmodifications in various obvious respects, all without departing fromthe invention. Accordingly, the drawing and description are to beregarded as illustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a summary of the present invention.

FIGS. 2A, 2B, 2C, and 2D are diagrams illustrating the basic concept ofthe present invention.

FIGS. 3A, 3B, 3C, and 3D are diagrams illustrating the basic concept ofthe present invention.

FIGS. 4A, 4B, 4C, and 4D are diagrams illustrating a comparativeexample.

FIG. 5 is a diagram illustrating a configuration example of a system ofan example embodiment of the present invention.

FIG. 6 is a diagram illustrating configuration examples of avirtualization control apparatus and servers of an example embodiment ofthe present invention.

FIG. 7 is a diagram illustrating a scale-up operation in an exampleembodiment of the present invention.

FIG. 8 is a diagram illustrating a scale-down operation in an exampleembodiment of the present invention.

FIG. 9 is a diagram illustrating an example of system switching (whenscale up is performed) in an example embodiment of the presentinvention.

FIG. 10 is a diagram illustrating an example of system switching (whenscale down is performed) in an example embodiment of the presentinvention.

FIG. 11 is a diagram illustrating NFV.

FIG. 12 is a diagram illustrating an example in which the presentinvention is applied to an NFV system.

PREFERRED MODES

After a basic configuration of the present invention is described first,an operating principle thereof and a comparative example will bedescribed and then example embodiments will be described. Furthermore,an example in which the present invention is applied to NFV (NetworkFunctions Virtualization) will be given.

<Basic Configuration of the Invention>

In FIG. 1, a system according to the present invention includes anactive system 101 that executes processing, a standby system 102 thatcan be scaled up and/or scaled down, and a control apparatus (controlmeans) 103 that controls system switching to switch the standby system102 undergoing the scale up or scale down to a new active system.

For example, the control apparatus 103 instructs the standby system 102to perform scale up or scale down, according to processing load or thelike of the active system 101 (or, an instruction, and settings from amaintenance apparatus not shown in the drawing). The control apparatus103 may be configured to receive a scaling (scale-up/scale-down)completion notification from the standby system 102 that has completedthe scale-up or scale-down, and control system switching o set thestandby system 102 undergoing the scaling (scale up/scale down) as thenew active system and set the active system 101 before the systemswitching, as a new standby system.

The control apparatus 103 may be configured to control the new standbysystem (original active system, becoming a new standby system by systemswitching) to perform scale up/scale down in the same way as the newactive system (original standby system that performs scale up/scale downbefore system switching).

The control apparatus 103 instructs the standby system 102 that hasscaled up to switch to an active system, for instance, as a result ofdetecting processing load of the active system 101 before the systemswitching, or when determining that scaling up is required based onsetting or instruction (e.g., input of a scaling up instruction) fromthe maintenance apparatus. For example, the system 101 (the originalactive system 101) that is to be set as a new standby system by systemswitching, may impose processing restriction on the system 102 (theoriginal standby system 102) that is to be set as a new active system.Upon reception of a scale-up completion notification from the newstandby system 101, the control apparatus 103 may release the processingrestriction imposed on the system 102 that is set as a new activesystem.

The control apparatus 103 imposes processing restriction on the originalactive system 101 before the system switching and instructs the originalstandby system 102 before the system switching to perform scale down,for instance, as a result of detecting that the original active system101 before the system switching has extra processing capabilities, orwhen determining that scaling down is required on the basis of settingsor an instruction (e.g., input of a scaling down instruction) from themaintenance apparatus. Upon reception of a scale-down completionnotification from the standby system 102 with the scaling downcompleted, the control apparatus 103 executes system switching, settingthe standby system 102 with the scaling down completed as a new activesystem. The new active system takes over, from the original activesystem 101, the processing restriction imposed on the original activesystem 101 before the system switching. The control apparatus 103 mayinstruct the new standby system 101 (the original active system 101) toperform scale down. Upon reception of a scale-down completionnotification from the new standby system 101, the control apparatus 103may release the processing restriction (taken over from the originalactive system 101) imposed on the system 102 (the original standbysystem 102) that is set as a new active system by the system switching.

Scaling up and scaling down may be executed by increasing or decreasingvirtual hardware resources such as a virtual CPU (virtual CentralProcessing Unit: vCPU) allocated to each virtual machine (VM) of theactive and standby systems. In this case, scale up is a technique ofincreasing processing performance by increasing CPU, memory, etc., of aserver allocated to the virtual machine (VM). Scaling down is atechnique of decreasing processing performance by reducing CPU, memory,etc., of a server allocated to the virtual machine (VM). Here, scale up(scale down) improves (reduces) processing performance of a computer byupgrading (downgrading) specifications of CPU, memory, etc., provided ina computer as a single entity such as a server. Scale out (scale in)improves (reduces) the processing performance of a system by increasing(decreasing) the number of computers, such as servers. Improving(reducing) the processing performance of a virtual system by increasing(decreasing) virtual machines (VM) on a server corresponds to scale out(scale in) in terms of the number of the virtual machines (VM). But,increasing (decreasing) virtual machines (VM) on a server consequentlyimproves (reduces) the processing performance of the server as a singleentity, this can be said to be (equivalent to) scale up (scale down) ofthe server.

Depending on congestion or margin of processing of the active system 101that performs session processing (e.g., call processing, etc.), thecontrol apparatus 103 may instruct the standby system 102 which is aswitching target of the active system, to perform scale up or scaledown.

Virtual machines (VM) on which applications operate as active andstandby applications, respectively, may be implemented on differentservers or on the same server. When implementing virtual machines (VM)on which applications operate as active and standby applications,respectively, on the same serve, out of a plurality of virtual machines(applications operating on the virtual machines) on the server, one ormore virtual machines (application(s) operating on the virtual machine)may each be configured to be an active system, and one or more othervirtual machine (application(s) operating on the virtual machine) mayeach be configured to be a standby system. The server (physical machine)may include a virtual network function (VNF) on the virtual machine andan NFVI (Network Functions Virtualization Infrastructure) forming anexecution infrastructure (virtualization infrastructure) for the VNF.The NFVI includes at least one of virtual computing, virtual storage,and virtual network configured by virtualizing at least one hardwareresource of computing, storage, and network functions using avirtualization layer such as a hypervisor (corresponding to physicalservers in FIG. 7, etc.). The server may include an OpenStack agent andits extension unit as a server agent. Moreover, in an application toNFV, active and standby systems may be configured by virtualizationdeployment units (VDU) on the NFVI.

<The Operating Principle of Scaling Up>

The operation of scale-up processing according to the present inventionwill be described with reference to FIGS. 2A, 2B, 2C, and 2D. FIGS. 2Aand 2B schematically illustrate virtual CPUs (virtual Central ProcessingUnit: vCPU) in virtual machines on an active system (ACT system) server1 and a standby system (SBY system) server 2, respectively, beforesystem switching. In other words, the active system server 1 and thestandby system server 2 comprise a virtual machine (VM) virtualized viaa hypervisor (HV) not illustrated in the drawings, and the virtualmachine comprises at least one virtual CPU (vCPU). FIGS. 2A and 2Billustrate virtual CPUs (vCPUs) allocated to a single virtual machine(VM) on the servers 1 and 2, respectively (virtual CPUs can be allocatedup to a maximum number that can be allocated to a virtual machine). Oneprocess is assigned to each virtual CPU (vCPU). The number of threadsthat can be processed in parallel in a virtual machine (VM) isproportional to the number of virtual CPUs. In FIGS. 2A and 2B, oneprocess is assigned to one virtual CPU (vCPU), for the sake ofsimplicity, however, a plurality of processes may be assigned to asingle virtual CPU (vCPU). Moreover, a hypervisor, a virtual machine(VM), a guest OS (Operating System), etc., on a server are omitted, onlyfor the sake of simplicity, in FIGS. 2A and 2B. A control apparatus (103in FIG. 1) that controls system switching is also omitted in FIGS. 2Aand 2B.

The standby system (SBY) in FIG. 2B is scaled up (in this case, two morevirtual CPUs (vCPUs) are increased (Hotadded), compared to the activesystem (ACT) executing processing (e.g., session processing) in FIG. 2A.Note that “Hot add” is a function to dynamically add CPU(s) or memory(s)to a running system. For example, in Hotadd, device(s) (vCPUs in thisexample) can be added without stopping the virtual machine (VM), whichis caused to recognize the added device(s) (vCPU).

The standby system (SBY) in FIG. 2B is configured as a hot standbysystem, and hence it is assumed that a process has been already assignedto each virtual CPU (vCPU) and data is synchronized with the activesystem (ACT) in FIG. 2A. Since the standby system (SBY) in FIG. 2B doesnot directly affect session processing, etc., a virtual machine (VM) canbe started up (restarting a guest OS or a process). Session managementfunction (HTTP (Hyper Text Transport Protocol) session) in SIP (SessionInitiation Protocol) or J2EE (Java (registered trademark) 2 Platform,Enterprise Edition) (Servlet) may be used to manage initiation andtermination of a session, though not limited thereto.

With the active system and the standby system being in states asillustrated in FIGS. 2A and 2B, respectively, when a system switching isexecuted, the standby system in FIG. 2B becomes a new active system(ACT) (FIG. 2D) and the active system in FIG. 2A a new standby system(SBY) (FIG. 2C). The new active system (the original standby system 2)in FIG. 2D takes over processing of the active system 1 (FIG. 2A),before the system switching, thereby making scale up of the processingperformance possible. Virtual machines may be dynamically scaled up orscaled down by increasing or decreasing the number of CPU cores, memorysuch as RAM (Random Access Memory), disks (HDD (Hard Disk Drive)), andnetwork interface controllers (NIC), in addition to the number ofvirtual CPUs (vCPUs). In other words, the dynamical scale up or scaledown of virtual machines may be done by increasing or decreasing atleast one of the number of virtual CPUs (the number of cores), virtualmemory capacity, virtual disk storage area (capacity), and the number orbandwidth of virtual NICs (network interface controllers).

<The Operating Principle of Scaling Down>

Next, the operation of scaling down will be described with reference toFIGS. 3A, 3B, 3C, and 3D. FIGS. 3A and 3B schematically illustratevirtual CPUs (vCPUs) in virtual machines on an active system (ACTsystem) server 1 and a standby system (SBY system) server 2,respectively, before system switching. Two virtual CPUs (vCPUs) havebeen deleted from the standby system (SBY) server 2 in FIG. 3B, ascompared with the active system (ACT) server 1 in FIG. 3A, and processesassigned to the deleted virtual CPUs (vCPUs) have the allocation tothese virtual CPUs (vCPUs) released and have terminated. With the activesystem and the standby system being in the states as illustrated inFIGS. 3A and 3B, when a system switching is executed, the standby systemin FIG. 3B becomes a new active system (FIG. 3D) and the active systemin FIG. 3A becomes a new standby system (FIG. 3C). As the new activesystem (ACT) (the original standby system 2) in FIG. 3D takes overprocessing of the active system 1 (FIG. 3A), before the systemswitching, the processing performance can be scaled down. Scaling down(Hotdel) the new standby system in FIG. 3C in the same way as the newactive system in FIG. 3D, does not cause any problem. The reason is thatsession processing (call processing, etc.) will not be affected, even ifthere is a restarting of a process. Note that “Hotdel” is a function todynamically delete CPUs or memory(s) from a running system. In thisexample, device(s) (e.g., vCPU(s), etc.) are deleted without stoppingthe virtual machine (VM).

COMPARATIVE EXAMPLE

FIGS. 4A and 4B are diagrams illustrating scale up and scale down of avirtual machine in Comparative Example (an example of a case where thepresent invention is no applied: the case where ACT/SBY system is notused).

FIG. 4B is a diagram schematically illustrating a virtual machine on aserver 1B scaled up by adding (Hotadd) virtual CPUs (vCPUs) to a server1A in FIG. 4A. In FIG. 4B, the server 1B only has the virtual CPUs(vCPUs) added (Hotadd) and cannot yet accomplish effective utilizationof resources. In other words, until processes are assigned to the addedvirtual CPUs (vCPUs) and started, the added virtual CPUs (vCPUs) do notcontribute to improvement of processing capability of the server 1B.

FIG. 4D is a diagram schematically illustrating a virtual machine (VM)on a server 1D scaled down by removing (Hotdel) virtual CPUs (vCPUs)from a server 1C in FIG. 4C. The server 1C executes processing using sixvirtual CPUs. When two virtual CPUs (vCPUs), as illustrated in FIG. 4Dare to be removed in a state in which processes and threads are stillassigned to these virtual CPUs (vCPUs), there is a case in which theprocesses assigned to the virtual CPUs may fail. Due to this processfailure, for example, a takeover (maintenance) of a session from avirtual machine on the server 1C to a virtual machine on the server 1Dmay fail as well, wherein the session has been done until then by thevirtual machine on the server 1C

As described, in Comparative Example that is not configured to haveactive and standby systems, when a virtual machine (VM) is scaled up,there is a delay before added virtual hardware resource (virtual CPU(s),etc.) starts contributing to improvement of processing performance(assigning a process to virtual CPU and so forth requires a time), as aresult of which efficient utilization of resources cannot be achieved.In the above described Comparative Example, when a virtual machine (VM)is scaled down, there is a possibility that a process may fail orsession takeover (maintenance) may fail, and this may become even afactor for inhibiting improvement of stability of the system and alsolead to service degradation. Note that improving (reducing) processingperformance of a virtual machine by increasing or decreasing virtual CPU(vCPU) corresponds to scale out (scale in) that increases or decreasesthe number of virtual CPU (vCPU), if focusing on virtual CPU (vCPU).However, since this consequently improves (reduces) processingperformance of a single virtual machine (VM), this can be an equivalentto perform scale up (scale down) of a virtual machine (VM).

EXAMPLE EMBODIMENTS

Next, Example Embodiments of the present invention will be described.

<System Configuration>

FIG. 5 is a diagram illustrating a configuration example of a system ofthe present example embodiment. In FIG. 5, an application (software)(Application: APL) 17 running on a virtual machine (VM) 15 on a server(physical machine: PM) 11 constitutes an active system (ACT system).More specifically, the server 11 includes hardware (HW) resources 13,such as computing hardware (e.g., CPU core), storage hardware (HDD, RAM(Random Access Memory), etc.), and network hardware, a virtualizationlayer 12 such as a hypervisor constituting a virtualization function, avirtual hardware resource 14 such as a virtual CPU (vCPU) obtained byvirtualizing the hardware resource 13 using the virtualization layer 12,and virtual machine(s) 15. In the virtual machine 15, application 17(ACT system) is executed on a guest OS 16 to implement a virtualizationnetwork function (VNF), for example, on a software basis. Though FIG. 5illustrates a plurality of the virtual machines 15 (two in FIG. 5), thenumber of the virtual machines 15 is not limited to the configuration inFIG. 5. Only for the sake of convenience of explanation, the virtualhardware resources 14 and 24, such as virtual CPUs (vCPUs) and so forth,are arranged on the virtualization layers 12 and 22 in parallel with thevirtual machines 15 and 25 in FIG. 5.

An application (software) (APL) 27 running on a virtual machine (VM) 25on a server (physical machine) 21 constitutes a standby system (SBYsystem). The basic configuration of the server 21 is the same as that ofthe active system server 11. In a case where the application 27 on thevirtual machine 25 of the standby system server 21 stands by, in a statewhere the current active system is scaled up, the virtual hardwareresources such as virtual CPUs (vCPUs) allocated to the standby systemare increased and processes are assigned to the added virtual CPUs(vCPUs) (refer to FIG. 2B). In a case where the application 27 on thevirtual machine 25 of the standby system server 21 stands by I a statewhere the current active system is scaled down, assignment of theprocesses to the virtual CPUs (vCPUs) of the virtual machine to beremoved is released, and then the virtual hardware resources, such asvirtual CPUs (vCPUs) and so forth, to be removed, are removed.

EMS (Element Management System) 10 is a maintenance management systemthat manages, configures, and maintains a virtual machine, for example.EMS 10 communicates with a virtualization control apparatus (alsoreferred to as “virtualization infrastructure”) 20.

The virtualization control apparatus 20 monitors and controls thevirtual machines 15 and 25 on the servers 11 and 21. That is, thevirtualization control apparatus 20 communicates with the virtualizationlayers 12 and 22 such as hypervisors of the servers 11 and 21, forexample, exchanges information regarding configuration and state of thevirtual machines (VM), and information regarding the configuration andstate of virtualized hardware resources, such as the virtual CPUsallocated to the virtual machines, performs deployment and control of avirtual machine, control of system switching, and communication with EMS10. The servers 11 and 21 are connected by a network 30, such as a LAN(Local Area Network), for example.

When applications on virtual machines of the servers 11 and 21 havingdifferent IP (Internet Protocol) addresses perform system switchingaccording a hot standby scheme and the application on the virtualmachine of a new active system server takes over an IP address of theserver having an original (before the system switching) activeapplication, an alias IP address may be taken over (the servers 11 and21 have the same alias IP address). Alternatively, LAN adapters of theservers may be switched. Or, such a scheme may be also adopted in whichan IP address is not taken over at a time of system switching.

In the example of FIG. 5, the applications (on the virtual machines) 17and 27 of the active and standby systems run on the different servers(physical machines) 11 and 21, but they may run on the same server.Furthermore, one or multiple combinations of a plurality of applicationsrunning on a plurality of virtual machines on a single server (physicalmachine) may be set to an active system, while remaining application maybe set to a standby system. A plurality of applications running on aplurality of virtual machines on a single server (physical machine) mayall be set to an active system, while a plurality of applicationsrunning on a plurality of virtual machines on another server (physicalmachine) all may be set to a standby system. A server withapplication(s) running on virtual machine(s) thereon being of an activesystem may be also referred to as an “active system server”, for thesake of simplicity. A server with application(s) running on virtualmachine(s) thereon being of a standby system may be also referred to asa “standby system server”, for the sake of simplicity.

<Correspondence Relation to the NFV Reference Architectural Framework>

FIG. 11 is cited from FIG. 4 in Chapter 7 of Non-Patent Literature 1, asa reference and illustrates NFV reference architectural frameworkdefined by NFV (Network Function Virtualization) ISG (IndustrySpecification Groups).

The servers 11 and 21 of the present example embodiment described withreference to FIG. 5 correspond to the NFV reference architecture asfollows.

In FIG. 11, VNFs (Virtual Network Functions) 1 to 3 correspond to, forexample, the applications operating on the virtual machines (VM) in FIG.5. For VNFs 1 to 3, network functions (e.g., MME (Mobility ManagementEntity), S-GW (Serving Gateway), P-GW (PDN Gateway), etc., in EPC(Evolved Packet Core) that is a core network of LTE (Long TermEvolution) network) may be implemented by software (virtual machine). InNFV ISG, a management function called EMS (Element Management System) isspecified for each VNF.

In the NFV reference architecture illustrated in FIG. 11, NFVI (NetworkFunction Virtualization Infrastructure) that constitutes animplementation infrastructure of each VNF is an infrastructure thatallows hardware resources (13 and 23 in FIG. 5) of a physical machine(server) such as computing, storage, and network functions to beflexibly handled as virtualized hardware resources (14 and 24 in FIG. 5)such virtualized computing, virtualized storage, virtualized network,and so on which have been virtualized using a virtualization layer (12and 22 in FIG. 5) such as a hypervisor.

Further, the virtualization control apparatus 20 in FIG. 5 can beassociated with NFV Management and Network Orchestration (MANO) of theNFV reference architecture in FIG. 11. In FIG. 11, NFV MANO includesNFV-Orchestrator (NFVO), VNF-Manager (VNFM), and VirtualizedInfrastructure Manager (VIM).

NFV-Orchestrator (NFVO) orchestrates and manages NFVI and VNF, andrealizes network service on NFVI (resource allocation to the VNF, andVNF management (auto-healing, auto-scaling, life cycle management ofVNF, etc.)).

VNF-Manager (VNFM) manages VNF's life cycle (instantiation, update,query, scaling, healing, termination, etc.).

Virtualized Infrastructure Manager (VIM) controls NFVI via avirtualization layer (computing, storage, network resource management,failure monitoring of NFVI that is an execution infrastructure of VNF,resource information monitoring, etc.).

Service, VNF and Infrastructure Description defines a template(descriptor) of information required for network services (NS) and VNFdeployment.

NSD (Network Service Descriptor): a template describing requirements andrestriction conditions for NS deployment.

VLD (Virtual Link Descriptor): a template describing resourcerequirements for a logical link that connects VNF and PNF constitutingNS.

VNFFGD (VNF Forwarding Graph Descriptor): a template describing logicaltopology and allocation of NS.

VNFD (VNF Descriptor): a template describing requirements andrestriction conditions for VNF deployment.

PNFD (Physical Network Function Descriptor): a template describingphysical network function connectivity, external interface, and KPIs(Key Performance Indicators) requirements of Virtual Link. NSD, VNFFGD,and VLD are included in an NS catalogue, while VNFD is included in anVNF catalogue.

OSS (Operations Support Systems) are a generic term for systems (such asapparatuses, software, and schemes) necessary for telecommunicationscarriers (carriers) to construct and manage services, for example. BSS(Business Support systems) are a generic term for information systems(such as apparatuses, software, and schemes) to be used for accountingfor and charging of a usage charge and handling of a customer by thetelecommunications carriers.

In FIG. 11, Os-Ma is a reference point between OSS (Operation ServiceSystems)/BSS (Business Service Systems) and NFV-MANO, and is used forlifecycle management request of network service, VNF lifecyclemanagement request, forwarding of NFV related state information,exchange of policy management, etc. A reference point Or-Vnfm is usedfor resource related requests (authorization, reservation, allocation,etc.) by VNF Manager (VNFM), forwarding of configuration information toVNFM, and collection of state information of VNF. A reference pointVi-Vnfm is used for resource allocation request from VNFM, such asquery, allocation/release, etc., of NFVI resource, and exchange ofvirtualized resource configuration and state information. A referencepoint Or-Vi is used for reservation/release, andallocation/release/update of NFVI resource by NFVO, and exchange ofvirtualized resource configuration and state information such asaddition/deletion/update of NFVI software image.

A reference point Ve-Vnfm is used for VNF lifecycle management request,and exchange of configuration information and state information betweenEMS and VNFM and between VNFM and VNFM. A reference point Nf-Vi is usedfor allocation of VM, along with instructions of computing/storageresource, updating VM resource allocation, VM migration, VM termination,assignment of virtualized resources in response to resource allocationrequests such as creating/deleting a connection between VMs, forwardingof virtualized resources state information, and exchange of hardwareresource configuration and state information. A reference point Se-Ma isused for information model query, etc., of NFV deployment template andNFV infrastructure. A reference point Vi-Ha interfaces a virtualizationlayer to hardware resources to create an execution environment for VNF,and collects state information for VNF management. A reference pointVn-Nf represents an execution environment provided by NFVI to VNF (referto Non-Patent Literature 1 for details).

<Configurations of Control Units of the Server and the VirtualizationControl Apparatus>

FIG. 6 is a diagram schematically illustrating control functions of thevirtualization control apparatus 20 and the servers 11 and 21 in FIG. 5,regarding scale up and scale down.

<Servers>

In FIG. 6, the server 11 includes a processing load monitor unit 111, asystem switching unit 112, processing restriction control unit 113, ascale-up execution unit 114, a scale-down execution unit 115, and acommunication control unit 116. Out of these, the processing loadmonitor unit 111, the system switching unit 112, and the processingrestriction control unit 113 may be implemented by processing ofapplications operating on the virtual machine (VM) 15 in FIG. 5, forexample. The scale-up execution unit 114 and the scale-down executionunit 115 may be implemented by processing of the virtualization layer 12(hypervisor) in FIG. 5.

The processing load monitor unit 111 monitors processing load of avirtual machine, and detects processing congestion and a processingmargin. When detecting processing congestion or a processing margin, theprocessing load monitor unit 111 notifies EMS 10 via a transmission unit(not illustrated) of the communication control unit 116.

The system switching unit 112 executes system switching. When theapplication 17 that runs on the virtual machine 15 on its own server 11is active, the system switching unit 112 switches the application 17 onthe server 11 to a standby system, and instructs the application 27 onthe server 21 to switch to an active system.

When the application 17 that operates as a standby system on the virtualmachine 15 on its own server 11, the system switching unit 112 switchesthe application 17 on the server 11 to an active system according to aninstruction received from a system switching unit of the server 21 inwhich the application 27 operates on the virtual machine 25 as an activesystem. When switching the application 17 operating on the virtualmachine 15 on its own server 11 from a standby system to an activesystem, the system switching unit 112 controls takeover of varioussettings, such as processing and execution environment, from theapplication 27 operating as an active system on the virtual machine 25.

When the application 17 operating on the virtual machine 15 on its ownserver 11 is switched from an active system to a standby system, theprocessing restriction control unit 113 instructs the application 27,which is to be switched from a standby system to a new active system, toimpose processing restriction, and, after completion of scale up in theown server 11, the application 27 switched to a new active system isinstructed to release the processing restriction.

When the application 17 operating on the virtual machine 15 on its ownserver 11 is switched from a standby system to an active system, theprocessing restriction control unit 113 releases processing restrictionon the application 17 on its own server 11, upon reception of a requestto release processing restriction from the virtualization controlapparatus 20 via the communication control unit 116.

Upon reception of a scale-up request from the virtualization controlapparatus 20 via the communication control unit 116 (a transmissionunit: not illustrated), the scale-up execution unit 114 increasesvirtual hardware resources (e.g., virtual CPUs) (14 in FIG. 5) to beallocated to a virtual machine. The scale-up execution unit 114 controlsprocess assignment to added virtual CPUs. The scale-up execution unit114 notifies the virtualization control apparatus 20 of scale-upcompletion via the communication control unit 116, after completion ofthe scale-up.

Upon reception of a scale-down request from the virtualization controlapparatus 20 via the communication control unit 116, the scale-downexecution unit 115 decreases virtual hardware resources (e.g., virtualCPUs) (14 in FIG. 5) allocated to a virtual machine. At this time, thescale-down execution unit 115 releases process assignment to the removedvirtual CPUs. The scale-down execution unit 115 notifies thevirtualization control apparatus 20 of scale-down completion via thecommunication control unit 116, after scale-down completion.

In the server 11, the processing load monitor unit 111, the systemswitching unit 112, and the processing restriction control unit 113 maybe implemented by, for example, processing of the application (APL) 17operating on the virtual machine (VM) 15 in FIG. 5. The scale-upexecution unit 114 and the scale-down execution unit 115 may be realizedby the processing of the virtualization layer 12 (hypervisor (HV)) inFIG. 5. Alternatively, in a virtualization scheme in which an OS(Operating System) called a management OS is made to operate as one ofvirtual machines (VMs), a device driver is provided in the managementOS, and an access from a virtual machine to a hardware is made via themanagement OS, each unit described above may be implemented on thevirtual machine of the management OS.

The server 21 is configured identically to the server 11. In the server21, a processing load monitor unit 211, the system switching unit 212,and processing restriction control unit 213 may be implemented by, forexample, processing of the application (APL) 27 operating on the virtualmachine (VM) 25 in FIG. 5. The scale-up execution unit 214 and thescale-down execution unit 215 may be implemented by processing of thevirtualization layer 22 (hypervisor (HV)) in FIG. 5. The servers areassumed to communicate with each other via (transmission/receptionunits, not illustrated, of) the communication control units 116 and 216of the servers 11 and 21.

A part or all of functions of the communication control units, thevirtualization layers, and the virtual machine server of the servers 11and 21 may be implemented by programs executed on processors (CPUs), notillustrated, constituting the servers 11 and 21, respectively. In thiscase, the processors each may implement each function by reading theprogram stored in a memory (semiconductor memory, HDD, etc.), notillustrated, provided in or connected to the servers 11 and 21 into amain memory and executing the program (instructions) by means ofsoftware, or in cooperation between software and hardware.

<Virtualization Control Apparatus>

In FIG. 6, the virtualization control apparatus 20 includes a sequencecontrol unit 201, a scale-up control unit 202, a scale-down control unit203, a system switching control unit 204, a communication control unit205 that controls communication with EMS 10, and a communication controlunit 206 that controls communication with the servers 11 and 21. Notethat the communication control units 205 and 206 are configured asseparate units in FIG. 6, but they can be merged into one communicationcontrol unit.

The sequence control unit 201 controls a sequence of scale-up andscale-down operations by activating the scale-up control unit 202, thescale-down control unit 203, and the system switching control unit 204,and providing required information thereto.

Upon reception of a notification of processing congestion or aprocessing margin in a virtual machine from the active system server outof the servers 11 and 21 via the communication control unit 206, thesequence control unit 201 controls a scale-up or scale-down sequence.

In a scale-up sequence, the sequence control unit 201 starts thescale-up control unit 202.

The scale-up control unit 202 instructs (the hypervisor (HV) of) thescale-up target server to execute scale up, such as increasing virtualCPUs, etc. Note that the scale-up control unit 202 may instructinformation such as the number of added virtual CPUs to the scale-upunit of the server.

Upon reception of a scale-up completion notification from, for example,the application switched from an active system to a standby system viathe communication control unit 206, the sequence control unit 201 startsthe system switching control unit 204.

The system switching control unit 204 instructs (an active applicationof) the server in which the application operates as an active system onthe virtual machine, to execute system switching via the communicationcontrol unit 206. The application of an active system, on reception of asystem switching instruction from the virtualization control apparatus20, transitions to a standby system, and then instructs (an applicationof a standby system of) the server in which the application operates asa standby system on the virtual machine, to transition to an activesystem.

Upon reception of a system switching completion notification from theapplication on the server, the sequence control unit 201 notifies EMS 10via the communication control unit 205 of a scale-up completionnotification.

In a scale-down sequence, the sequence control unit 201 starts thescale-down control unit 203.

The scale-down control unit 203 instructs (the hypervisor (HV) of) thescale-down target server to perform scale down by decreasing virtualCPUs. Note that the scale-down control unit 203 may instruct informationsuch as the number of decreased virtual CPUs to the scale-down unit(hypervisor (HV)) of the server.

Upon reception of a scale-down completion notification from the serverin which an application operates on the virtual machine as a standbysystem, via the communication control unit 206, the sequence controlunit 201 starts the system switching control unit 204.

The system switching control unit 204 instructs (an active applicationof) the server in which an application operates on the virtual machineas an active system, to execute system switching via the communicationcontrol unit 206. The application of an active system, upon reception ofthe system switching instruction from the virtualization controlapparatus 20, transitions to a standby system, and then instructs theapplication of a (original) standby system before the system switchingto transition to an active system.

Upon reception of a system switching completion notification from theapplication undergoing switching from an active system to a standbysystem, for example, the sequence control unit 201 notifies EMS 10, viathe communication control unit 205, of scale down completionnotification.

At part or all of functions of at least a part of the units 201 to 206of the virtualization control apparatus 20 may be implemented by aprogram executed by a processor (CPU), not illustrated, constituting thevirtualization control apparatus 20. In this case, the processor mayimplement each function by reading, into a main memory, a program storedin a memory (semiconductor memory, HDD, etc.), not illustrated, providedin or connected to the virtualization control apparatus 20 and executingthe program (instructions), by means of software or in cooperation ofsoftware and hardware.

<Scale-Up Sequence>

FIG. 7 is a diagram schematically illustrating an example of a scale-upsequence in the system of the Example Embodiment described withreference to FIGS. 5 and 6.

In FIG. 7, the physical servers 11 and 21 correspond to the servers(physical machines: PM) 11 and 21 in FIGS. 5 and 6. It should be notedthat the physical servers 11 and 21 are for specifying that the serversare physical machines (PM) (the servers 11 and 21 are different devices(units)) and they will be simply referred to as the servers 11 and 21hereinafter. FIG. 7 illustrates the virtualization layers 12 and 22 inFIG. 6, as hypervisors (HV) 12 and 22, respectively. “VM ACT” and “VMSBY” denote applications of an active system (ACT) and a standby system(SBY) on virtual machines (VM), respectively. The applications may beVDUs (Virtualization Deployment Units) of NFV or the like. “VM ACT” and“VM SBY” may be VMs of an active system and a standby system,respectively. In FIG. 7, numbers (step numbers) are given to typicalsequences, for the sake of explanation. The same may be said in FIGS. 8to 10 described later.

The processing load monitor unit 111 of the server 11 detects processingcongestion in an application operating on the virtual machine (S1).

The processing load monitor unit 111 of the server 11 notifies thevirtualization control apparatus 20 of congestion detection (S2).

Upon reception of a notification of congestion detection, the sequencecontrol unit 201 in the virtualization control apparatus 20 notifies EMS10 of the congestion in the application on the server 11 and of start ofa scale-up (S3).

The sequence control unit 201 of the virtualization control apparatus 20starts the scale-up control unit 202, which then instructs the server 21(hypervisor (HV)) in which the application 27 operates on the virtualmachine 25 as a standby system (SBY), to execute scale up (Hotadd) (S4).

Upon reception of the scale-up instruction, the scale-up execution unit214 (e.g., implemented on the hypervisor (HV)) of the server 21 executeshot-add processing (S5), increases virtual CPUs (vCPUs) to be allocatedto the virtual machine 25 on which the application 27 of a standbysystem (SBY) runs (adding vCPUs), assigns processes to these virtualCPUs (vCPUs), and transmits a scale-up completion notification (Hotaddcompletion notification) to the virtualization control apparatus 20(S6).

Upon reception of the scale-up (hot-add) completion notification, thesequence control unit 201 of the virtualization control apparatus 20starts the system switching control unit 204, which then transmits asystem switching instruction to the system switching unit 112 (e.g., anapplication on the VM) of the server 11 in which the applicationoperates on the virtual machine as an active system (ACT) (S7).

In response to the system switching instruction, system switching of theapplications is performed between the servers 11 and 21 (S8). The systemswitching unit 112 of the server 11 in which the application 17 operateson the virtual machine 15 as an active system (ACT), switches theapplication 17 to a standby system (SBY), and instructs the server 21 inwhich the application 27 operates on the virtual machine 25 as a standbysystem (SBY), to transition to an active system (ACT), for example. As aresult, the system switching unit 212 of the server 21, in which theapplication 27 operates on the virtual machine 25 as a standby system(SBY), sets the application 27 to an active system (ACT) (switches theapplication 27 from a standby system to an active system).

The server 11 (the application 17 thereof) in which the application 17operating on the virtual machine 15 is switched from an active system(ACT) to a standby system (SBY) as a result of the system switching,notifies the virtualization control apparatus 20 of completion of systemswitching (S9).

The sequence control unit 201 of the virtualization control apparatus20, upon reception of notification of the completion of systemswitching, transmits a scale-up completion notification to tEMS 10(S10).

<Scale-Down Sequence>

FIG. 8 is a diagram schematically illustrating an example of ascale-down sequence in the system of the example embodiment describedwith reference to FIGS. 5 and 6.

In FIG. 8, the physical servers 11 and 21 correspond to the servers(physical machines: PM) 11 and 21 in FIGS. 5 and 6. The hypervisors (HV)12 and 22 in FIG. 8 correspond to the virtualization layers 12 and 22 inFIGS. 5 and 6. In FIG. 8, “VM ACT” and “VM SBY” denote the applicationsof an active system (ACT) and a standby system (SBY) on the virtualmachines (VM), respectively. “VM ACT” and “VM SBY” may be VMs of anactive system (ACT) and a standby system (SBY), respectively. In FIG. 8,numbers (step numbers) are given to typical sequences, for the sake ofexplanation.

The processing load monitor unit 111 of the server 11 detects processingmargin in the virtual machine (S21).

The processing load monitor unit 111 of the server 11 determines thatscale-down is possible due to the processing margin and notifies thevirtualization control apparatus 20 (S22).

Upon reception of the notification from the server 11, the sequencecontrol unit 201 in the virtualization control apparatus 20 notifies EMS10 of start of scale down in the server 11 (S23).

The sequence control unit 201 of the virtualization control apparatus 20starts the scale-down control unit 203, which then instructs the server21 (hypervisor (HV)) in which the application 27 operates on the virtualmachine 25 as a standby system (SBY), to execute scale down (Hotdel)(S24).

Upon reception of the scale-down instruction, the scale-down executionunit 215 (e.g., the hypervisor (HV)) of the server 21 executes Hotdel(Hotdel) (S25), removes virtual CPUs (vCPUs) allocated to the virtualmachine 25, on which the application 27 of a standby system (SBY) runs,releases process assignment, and transmits a scale-down (Hotdel)completion notification to the virtualization control apparatus 20(S26).

Upon reception of the scale-down (Hotdel) completion notification, thesequence control unit 201 of the virtualization control apparatus 20starts the system switching control unit 204, which then transmits asystem switching instruction to the application 17 on the virtualmachine 15 on the server 11 (S27).

The system switching of the applications is performed between theservers 11 and 21 (S28). The system switching unit 112 of the server 11in which the application 17 operates on the virtual machine 15 as anactive system (ACT), switches the application 17 to a new standby system(SBY), and instructs the server 21 in which the application 27 operateson the virtual machine 25 as a standby system (SBY), to switch to anactive system (ACT), for example. As a result, the system switching unit212 of the server 21 sets the application 27 to an active system (ACT)(switches the application 27 from a standby system to an active system).

The server 11 in which the application 17 on the virtual machine (VM) 15switches to a standby system (SBY) as a result of the system switching,notifies the virtualization control apparatus 20 of completion of thesystem switching (S29).

The sequence control unit 201 of the virtualization control apparatus20, upon reception of a notification of completion of the systemswitching, transmits a scale-down completion notification to EMS 10(S30).

<System Switching: Scale-Up>

FIG. 9 is a diagram illustrating in detail an example of the systemswitching sequence (S8) in FIG. 7.

In FIG. 9, sequences (step numbers) from S1 to S7 are the same as inFIG. 7. Although the virtualization control apparatus 20 transmits arequest to a physical server 21 of a standby system (SBY) to executescale up (Hotadd), upon reception of a notification of congestiondetection in the virtual machine on the physical server 11 in FIG. 7,triggered by a request from a maintenance operator (e.g., EMS 10), thevirtualization control apparatus 20 may transmit a request to thephysical server 21 of a standby system (SBY) to execute scale up(Hotadd).

Upon reception of the system switching instruction from thevirtualization control apparatus 20, the system switching unit 112 ofthe server 11 with the application 17 operating thereon as an active(ACT) system, switches the application 17 to a standby system (SBY)(S8-1). It is noted that the virtualization control apparatus 20communicates with the hypervisors (HVs) of the servers 11 and 21.

The server 11 in which the application 17 on the virtual machine (VM) 15is newly switched to a standby system (SBY), transmits a request (ACTtransition request) to transition to an active system, to theapplication 27 on the virtual machine (VM) 25 on the server 21 (ACT)(S8-2). In the system switching of the application 17 from an activesystem (ACT) to a standby system (SBY), the server 11 may set flaginformation indicating whether the application 17 is currently of anactive system (ACT) or a standby system (SBY) to “standby (SBY)” thoughnot limited thereto. The server 11 may save, in a predetermined storagearea, information necessary for the application 27 that becomes a newlyactive system (ACT), to take over information, such as an executionenvironment, setting parameter information, data, etc., of theapplication 17 that has been hitherto of an active system (ACT), andforward the information to the server 21 in which the application 27 isswitched to a newly active system (ACT).

In the server 21, upon reception of the ACT transition request from theapplication 17 of the server 11, the system switching unit 212 sets theapplication 27 to an active system (ACT) (S8-3).

The application 27 of the server 21 that has become a newly activesystem (ACT) transmits an ACT transition completion notification to theserver 11 (S8-4).

Upon reception of the ACT transition completion notification from theserver 21, the application 17 on the virtual machine 15 on the server 11transmits a notification that the application 17 on the server hastransitioned to a standby system (SBY) (SBY transition completion) and acall processing restriction request to the server 21 (S8-5).

Upon reception of the call processing restriction request from theserver 11, the processing restriction control unit 213 of the server 21may restrict call processing performed by the virtual machine (S8-6).This restricts an amount of call processing, during system switching, sothat any additional call processing is not accepted, until scaled up ofboth the standby (SBY) and active (ACT) systems are completed.

The processing restriction control unit 213 of the server 21, uponcompletion of setting of the call processing restriction, notifiescompletion of the call processing restriction request to the server 11(S8-7).

In the server 11 (in which the application 17 is switched to a newstandby system), upon reception of the completion of call processingrestriction request, the system switching unit 112 notifies thevirtualization control apparatus 20 of completion of the systemswitching (S8-8).

The virtualization control apparatus 20 transmits a scale-up (Hotadd)request to the server 11 (hypervisor (HV)) in which the application 17operates on the virtual machine 15 as a standby system (SBY) (S8-9). Ina hot standby redundant system, data replication is performed between anactive system (ACT) and a standby system. Therefore, if scale up isexecuted in the server 21 alone (server with the application operatingon the virtual machine and switched to a new active system), there isperformance difference, such that scale up (Hotadd) is also executed inthe server 11 (hypervisor (HV)) in which the application 17 has justbecome a standby system (SBY), in order for processing not to beaffected by performance difference between apparatuses before scale-upand after scale up.

The scale-up execution unit 114 of the server 11 increases (Hotadd)virtual CPUs allocated to the virtual machine (VM) 15 on which theapplication 17 runs (S8-10). At this time, virtual memory, virtualstorage, bandwidth of a virtual network, the number of installed virtualNICs, etc., allocated to the virtual machine may, as a matter of course,be increased.

The scale-up execution unit 114 of the server 11 transmits a scale-up(Hotadd) completion notification to the virtualization control apparatus20 (S8-11).

The virtualization control apparatus 20 transmits a request to releasethe call processing restriction to the server 21 (S8-12). The processingrestriction control unit 213 of the server 21 releases the callprocessing restriction (S8-13). Since the new active system (ACT) andthe new standby system (SBY) have completed scale up, the new activesystem is allowed to accept a further amount of call processingcorresponding to perform scale up (increase). The processing restrictioncontrol unit 213 of the server 21 transmits a notification of completionof call processing restriction release to the virtualization controlapparatus 20 (S8-14).

The virtualization control apparatus 20, upon reception of thenotification of completion of call processing restriction release,transmits a scale-up completion notification to EMS 10 (S20).

In the example of FIG. 9, the virtualization control apparatus 20transmits the call processing restriction release request to (theapplication, that runs on the virtual machine and becomes a new activesystem, of) the server 21 (S8-12), however, the server 11 that hascompleted scale-up (Hotadd) may transmit the call processing restrictionrelease request to the server 21. In this case, the server 21 that hasreleased the call processing restriction, transmits a call processingrestriction release completion notification to the server 11, the server11, upon reception of the call processing restriction release completionnotification, transmits a system switching completion notification tothe virtualization control apparatus 20, in accordance with to S9 inFIG. 7. The virtualization control apparatus 20, upon reception of thesystem switching completion notification, transmits a scale-upcompletion notification to EMS 10. In FIG. 9, as the processingrestriction of the virtual machine (the application running thereon) onthe server of a new active system, restriction imposed on callprocessing (e.g., VoIP (Voice over IP)) and release thereof aredescribed, but processing selected as a target for restriction in thevirtual machine (application running thereon) on the server of a newactive system (ACT) may, as a matter of course, be any one other thanthe call processing.

<System Switching: Scale-Down>

FIG. 10 is a diagram illustrating in detail an example of the systemswitching sequence (S28) in FIG. 8. Note that steps S24 to S27 and S30in FIG. 10 correspond to S24 to S27 and S30 in FIG. 8, respectively.

In FIG. 8, after detecting a processing margin, the server 11 transmitsa judgment that scale-down is possible to the virtualization controlapparatus 20, which in turn instructs the server 21 to perform scaledown while, in the example of FIG. 10, EMS 10 in FIG. 7 instructs andrequests the virtualization control apparatus 20 to execute scale down(S20A).

The virtualization control apparatus 20, upon reception of thescale-down request, transmits a call processing restriction releaserequest to the server 11 in which the application 17 operates on thevirtual machine (VM) 15 as an active system (ACT) (S20B). The processingrestriction control unit 113 of the server 11 restricts call processingperformed by the virtual machine (VM) (S20C). Call processingrestriction (reduction) is performed in advance so that call processingafter the scale-down will not suffer from congestion responsive to anamount that is before the scale-down.

The server 11 transmits a call processing restriction completionnotification to the virtualization control apparatus 20 (S20D).

Triggered by the scale-down request from EMS 10, the virtualizationcontrol apparatus 20 requests the server 21 (hypervisor (HV)) in whichthe application 27 operates on the virtual machine (VM) as a standbysystem (SBY), to execute scale down (Hotdel) (S24). The scale-downexecution unit 215 of the server 21 removes virtual CPUs (vCPUs)allocated to the virtual machine (VM), on which the application of astandby system (SBY) runs (S25). At this time, virtual memory, virtualstorage, bandwidth of a virtual network, the number of installed virtualNICs, etc., allocated to the virtual machine may be decreased. Whenremoving relevant virtual CPUs (vCPUs), the scale-down execution unit215 of the server 21 in which the application operates on the virtualmachine (VM) as a standby system (SBY), releases process assignment tothe relevant virtual CPUs (vCPUs) and then removes the relevant virtualCPUs (vCPUs).

The server 21 transmits a scale-down completion notification (Hotdelcompletion notification) to the virtualization control apparatus 20(S26).

The virtualization control apparatus 20 instructs the server 11 toexecute system switching (S27).

Upon reception of the system switching instruction from thevirtualization control apparatus 20, the system switching unit 112 ofthe server 11 sets the application 17 operating on the virtual machine(VM) 15 on the server 11 to a standby system (SBY) (S28-1).

The server 11 transmits a request (ACT transition request) to the server21 for the application 27 operating on the virtual machine (VM) 25 totransition to the active system (ACT) (S28-2).

The system switching unit 212 of the server 21 sets the application 27operating on the virtual machine (VM) 25 on the server 21 to an activesystem (ACT) (S28-3). The application 27 of the server 21 that has newlybecome an active system (ACT) takes over operating environment, settinginformation, etc., of the application 17 on the server 11, which was ofan active system (ACT) before the system switching. In this example, thecall processing restriction requested by the virtualization controlapparatus 20 and imposed on the application 17 on the virtual machine15, which was of an active system (ACT) before the system switching, istaken over by the application 27 on the virtual machine, which has newlybecome active (ACT).

The server 21 having the newly active system (ACT) application 27operating on the virtual machine (VM) 25 transmits an ACT transitioncompletion notification to the server 11 (S28-4).

Upon reception of the ACT transition completion notification, the server11 notifies the server 21 that the application 17 on the virtual machine15 on the server 11 of completion of transition to the standby system(S28-5).

The server 11 notifies the virtualization control apparatus 20 ofcompletion of the system switching (S28-6).

The virtualization control apparatus 20 transmits a scale-down (Hotdel)request to the server 11 in which the application 17 operates on thevirtual machine 15 as a standby system (SBY) (S28-7). In a hot standbyredundant system, data replication is performed between the activesystem (ACT) and standby systems, for example. Therefore, if scale downis executed in the virtual machine in one of the server alone (server inwhich the application on the virtual machine has become a new activesystem), there is performance difference, such that scale down (Hotdel)is also executed in the virtual machine of the other one of the serversin which the application has just become a standby system (SBY), inorder for processing not to be affected by performance differencebetween apparatuses before scale-up and after scale up.

The scale-down execution unit 115 (e.g., implemented on the hypervisor(HV)) of the server 11 decreases (Hotdel) virtual CPUs allocated to thevirtual machine 15 with the application 17 operating thereon as astandby system (SBY) (S28-8). At this time, the scale-down executionunit 115 of the server 11 decreases (Hotdel) virtual CPUs, afterreleasing process assignment to these virtual CPUs.

The server 11 transmits a scale-down (Hotdel) completion notification tothe virtualization control apparatus 20 (S28-9).

The virtualization control apparatus 20 transmits a call processingrestriction release request to the server 21 (S28-10). The processingrestriction control unit 213 of the server 21 releases the callprocessing restriction (S28-11). With completion of scale down of theapplications operating on the virtual machines (VMs) (a new activesystem (ACT) and a new standby system (SBY)), the call processingrestriction imposed by the processing restriction control unit 213 isreleased in the new active system. The server 21 transmits anotification of completion of the call processing restriction release tothe virtualization control apparatus 20 (S28-12).

The virtualization control apparatus 20, upon reception of notificationof completion of the call processing restriction release, transmits ascale-down completion notification to the EMS 10 (S30). In the exampleof FIG. 10, the virtualization control apparatus 20 transmits a callprocessing restriction release request to the server 21 (S28-10), but,the server 21 may transmit the call processing restriction releaserequest to the server 11, which may then transmit a system switchingcompletion notification to the virtualization control apparatus 20 inaccordance with the sequence number 29 in FIG. 8, and the virtualizationcontrol apparatus 20, upon reception of the system switching completionnotification, may transmit a scale-down completion notification to EMS10.

In FIG. 10, as an example of the processing restriction of theapplications operating on the virtual machines on the servers of anactive system before the system switching and of a new active system,restriction imposed on call processing (e.g., VoIP (Voice over IP)) andrelease thereof are described, but processing selected as a target forrestriction in the application operating on the virtual machine on theserver of a new active system may, as a matter of course, be any oneother than the call processing.

FIG. 12 is a diagram illustrating an example in which scale controllingusing a redundant system according to the above described presentexample embodiment is applied to an NFV system. In an example of FIG.12, OpenStack and an extension unit constitute VIM in FIG. 11. Anorchestrator II that performs VNF life cycle management, configurationinformation management, and state monitoring constitutes VNFM in FIG.11. An orchestrator I in FIG. 12 includes an identity manager, a globalresource orchestrator, a local resource orchestrator, an Operations andMaintenance (O&M) integrated manager, template management, and a serviceorchestrator. The details of the orchestrator I (corresponding to NVFO)will be omitted. Regarding configuration and functions of NVFO, inaddition to the related description of FIG. 11, reference may be made asappropriate to Non-Patent Literature 1 for details.

OpenStack includes:

Nova (VM network resource control, etc.)/Glance (image management ofguest OS, etc.);

Neutron (control and configuration management of virtual network used byVM); and

Ceilometer (measurement and monitoring of resource usage amount ofNFVI).

For example, Nova/Glance controls start/termination of VM, VM migration,management of VM resource information, etc. Neutron controls creation ofa virtual network and attachment of the virtual network. Ceilometercontrols collection of VM resource usage status, management ofnotification policy (notification from NFVO), notification to NFVO, etc.

Though not limited thereto, the extension unit includes, for example:

A physical machine (PM) controller that performs control of physicalmachine(s) (PM(s)) and resource management;

A virtual machine (VM) controller that performs control of deployment ofvirtual machine(s) (VM(s)) (PM selection, etc.);

A network controller that performs management control such as monitoringfailure of a virtual network used by a virtual machine, resourcemanagement, etc.; and

Resource monitoring that performs monitoring of NFVI resources on aserver (e.g., collecting failure information and resource usage statusof physical machine(s) (PM(s)) and virtual machine(s) (VM(s)),notification policy management (instructions from NFVO), andnotification to NFVO) and so forth.

Servers 11 and 21 in FIG. 12 correspond to the servers 11 and 21 in FIG.5. The servers 11 and 21 may each include agents of OpenStack and theextension unit. In the servers 11 and 21, HV denotes hypervisor, VMdenotes virtual machine, and HW/OS denotes hardware resources and OS.VNFs (Virtual Network Functions) on the servers 11 and 21 correspond tothe applications on the virtual machines in FIG. 5. VNF may be VDU(Virtualization Deployment Unit).

The functions (scale-up/scale-down control, system switching control,etc.) of the virtualization control apparatus 20 in FIG. 5 can beimplemented on the controllers in OpenStack and the extension unitcorresponding to VIM, or on the orchestrator corresponding to the VNFMin FIG. 12, for example. FIG. 12 illustrates a configuration in whichthe servers are duplicated, corresponding to that in FIG. 5. However,such a configuration in which at least one application (VNF, VDU) out ofa plurality of applications (VNFs, VDUs) running on a plurality ofvirtual machines on a server is an active system and at least anotherapplication (VNF, VDU) is of a standby system may be employed.Alternatively, a configuration in which one or more VMs are of an activesystem and another one or more VMs are of a standby system may be used.

Each disclosure of the above-listed Non Patent Literature isincorporated herein by reference. Modification and adjustment of eachexample embodiment or each example are possible within the scope of theoverall disclosure (including the claims) of the present invention andbased on the basic technical concept of the present invention. Variouscombinations and selections of various disclosed elements (includingeach element in each claim, each element in each example, each elementin each drawing, and so on) are possible within the scope of the claimsof the present invention. That is, the present invention naturallyincludes various variations and modifications that could be made bythose skilled in the art according to the overall disclosure includingthe claims and the technical concept.

The invention claimed is:
 1. A node system comprising: a first computerthat executes processing when operating as an active system of aredundant system; a second computer that is able to perform at least oneof scale-up and scale-down when operating as a standby system of theredundant system; and a controller that issues an instruction to thesecond computer operating as the standby system to perform the scale-upor the scale-down, when the active system needs to be scaled-up orscaled-down, wherein the second computer operating as the standbysystem, responsive to the instruction, in case of performing thescale-up, increases the number of virtual CPUs (Central ProcessingUnits) included in the second computer and allocates one or moreprocesses to one or more virtual CPUs added, while in case of performingthe scale-down, the second computer decreases the number of virtual CPUsincluded in the second computer and releases allocation of one or moreprocesses allocated to one or more virtual CPUs deleted, and transmits acompletion notification to the controller when the scale-up or thescale-down is completed, and wherein, upon reception of the completionnotification of the scale-up or the scale-down from the second computerof the standby system, the controller controls to execute systemswitching of the redundant system to switch the second computeroperating as the standby system undergoing the scale-up or scale-down toa new active system and to switch the first computer operating as theactive system to a new standby system.
 2. The node system according toclaim 1, wherein the controller controls the first computer of the newstandby system to perform scale-up or scale-down in the same way as thesecond computer of the standby system before switching to the new activesystem.
 3. The node system according to claim 1, wherein the controllerdetermines whether the active system needs to be scaled up or scaleddown, based on processing load in the active system.
 4. The node systemaccording to claim 1, wherein the first and second computers areconstituted by first and second server apparatuses, or, the first andsecond computers are included in a same server apparatus.
 5. The nodesystem according to claim 4, wherein the server apparatus comprises: avirtual network function (VNF) implemented by software and operating ona virtual machine; and an NFVI (Network Functions VirtualizationInfrastructure) that provides an execution infrastructure for the VNF,and wherein the NFVI includes at least one of virtualized computing,storage, and network resources obtained by virtualizing, with avirtualization layer, at least one of hardware computing, storage, andnetwork resources.
 6. A node system comprising: a first computer thatexecutes processing when operating as an active system of a redundantsystem; a second computer that is able to perform at least scale-up,when operating as a standby system of the redundant system; and acontroller that issues an instruction to the second computer operatingas the standby system to perform scale-up when the active system needsto be scaled-up, wherein the second computer operating as the standbysystem, responsive to the instruction, in performing the scale-up,increases the number of virtual CPUs (Central Processing Units) includedin the second computer and allocates one or more processes to one ormore virtual CPUs added, and transmits a scale-up completionnotification to the controller when the scale-up is completed, wherein,upon reception of the scale-up completion notification from the secondcomputer of the standby system that completes the scale-up, thecontroller controls to execute system switching of the redundant systemto switch the second computer operating as the standby system undergoingthe scale-up to a new active system, and to switch the first computeroperating as the active system before the system switching to a newstandby system, wherein after the system switching, the first computerof the new standby system imposes a processing restriction on the secondcomputer of the new active system, wherein the controller instructs thefirst computer of the new standby system to perform scale-up in the sameway as the second computer of the standby system that transitions to thenew active system, and wherein the controller, upon reception of ascale-up completion notification from the first computer of the newstandby system, releases the processing restriction imposed on the firstcomputer of the new active system.
 7. A node system comprising: a firstcomputer that executes processing when operating as an active system ofa redundant system; a second computer that is able to perform at leastscale-down, when operating as a standby system of the redundant system;and a controller that imposes a processing restriction on the firstcomputer of the active system and then issue an instruction to thestandby system to perform scale-down, when the active system needs to bescaled down, wherein the second computer operating as the standbysystem, responsive to the instruction, in performing the scale-down,decreases the number of virtual CPUs included in the second computer andreleases allocation of one or more processes allocated to one or morevirtual CPUs deleted, and transmits a scale-down completion notificationto the controller when the scale-down is completed, wherein thecontroller, upon reception of the scale-down completion notificationfrom the second computer of the standby system, controls to execute thesystem switching of the redundant system to switch the second computeroperating as the standby system undergoing the scale-down to a newactive system and to switch the first computer operating as the activesystem to a new standby system, wherein the controller, after the systemswitching, instructs the first computer of the new standby system toperform scale-down in the same way as the second computer of the standbysystem becoming the new active system, and wherein the controllerreleases the processing restriction imposed on the second computer ofthe new active system, upon reception of a scale-down completionnotification from the first computer of the new standby system.
 8. Aserver apparatus comprising: a processor; and a memory storing programinstructions executable by the processor, wherein the processor isconfigured to execute: a redundant system constituted by an activesystem and a standby system, wherein the active system executesprocessing and the standby system is able to perform at least one ofscale-up and scale-down; and a control process that issues aninstruction to the standby system to perform the scale-up or thescale-down, when the active system needs to be scaled-up or scaled-down,wherein the standby system, responsive to the instruction, in case ofperforming the scale-up, increases the number of virtual CPUs (CentralProcessing Units) included in the standby system and allocates one ormore processes to one or more virtual CPUs added, while in case ofperforming the scale-down, the standby system decreases the number ofvirtual CPUs included in the standby system and releases allocation ofone or more processes allocated to one or more virtual CPUs deleted, andtransmits a completion notification to the control process when thescale-up or the scale-down is completed, and wherein the controlprocess, upon reception of the completion notification from the standbysystem, controls to execute system switching of the redundant system toswitch the standby system undergoing the scale-up or scale-down to a newactive system and to switch the active system to a new standby system.9. A server apparatus comprising: a processor; and a memory storingprogram instructions executable by the processor, wherein the processoris configured to execute: a redundant system constituted by an activesystem and a standby system, wherein the active system executesprocessing and the standby system is able to perform at least scale-upout of scale-up and scale-down; and a control process that issues aninstruction to the standby system to perform the scale-up when theactive system needs to be scaled-up, wherein the standby system,responsive to the instruction, in performing the scale-up, increases thenumber of virtual CPUs (Central Processing Units) included in thestandby system and allocates one or more processes to one or morevirtual CPUs added, and transmits a scale-up completion notification tothe control process when the scale-up is completed, wherein, uponreception of the scale-up completion notification from the standbysystem that completes the scale-up, the control process controls toexecute system switching of the redundant system to switch the standbysystem undergoing the scale-up to a new active system, and to switch theactive system before the system switching to a new standby system,wherein after the system switching, the new standby system imposes aprocessing restriction on the new active system, wherein the controlprocess instructs the new standby system to perform scale-up in the sameway as the standby system that transitions to the new active system, andwherein the control process, upon reception of a scale-up completionnotification from the new standby system, releases the processingrestriction imposed on the new active system.
 10. A server apparatuscomprising: a processor; and a memory storing program instructionsexecutable by the processor, wherein the processor is configured toexecute: a redundant system constituted by an active system and astandby system, wherein the active system executes processing and thestandby system is able to perform at least scale-down of scale-up andthe scale-down; and a control process that imposes a processingrestriction on the active system and then issue an instruction to thestandby system to perform scale-down, when the active system needs to bescaled down, wherein the standby system, responsive to the instruction,in performing the scale-down, decreases the number of virtual CPUsincluded in the standby system and releases allocation of one or moreprocesses allocated to one or more virtual CPUs deleted, and transmits ascale-down completion notification to the control process when thescale-down is completed, wherein, upon reception of the scale-downcompletion notification from the standby system, the control processcontrols to execute the system switching of the redundant system toswitch the standby system undergoing scale-up or scale-down to a newactive system and to switch the active system to a new standby system,wherein the control process, after the system switching, instructs thenew standby system to perform scale-down in the same way as the standbysystem becoming the new active system, and wherein the control processreleases the processing restriction imposed on the new active system,upon reception of a scale-down completion notification from the newstandby system.
 11. A scaling control method of an active system of aredundant system executing processing and a standby system of theredundant system being able to perform at least one of scale-up andscale-down, the scaling control method comprising: issuing, by a controlapparatus, an instruction to the standby system to perform scale-up orscale-down, when the active system needs to be scaled-up or scaled-down;increasing, by the standby system, responsive to the instruction and incase of performing the scale-up, the number of virtual CPUs (CentralProcessing Units) included in the standby system and allocating one ormore processes to one or more virtual CPUs added; decreasing, by thestandby system, responsive to the instruction and in case of performingthe scale-down, the number of virtual CPUs included in the standbysystem and releasing allocation of one or more processes allocated toone or more virtual CPUs deleted; transmitting a completion notificationto the control apparatus, when the scale-up or scale-down is completed;and upon reception of the completion notification from the standbysystem, controlling, by the control apparatus, to execute systemswitching to switch the standby system undergoing the scale-up orscale-down to a new active system and to switch the active system beforethe system switching to a new standby system.
 12. The scaling controlmethod according to claim 11, comprising: performing scale-up orscale-down of the new standby system in the same way as the standbysystem that transitions to the new active system.
 13. The scalingcontrol method according to claim 11, comprising: determining whetherscale-up or scale-down is necessary, depending on processing load in theactive system; and performing scale-up or scale-down for the standbysystem and the active system, when it is determined that scale-up orscale-down is necessary.
 14. The scaling control method according toclaim 11, wherein the active system and the standby system areconstituted by different server apparatuses, or the active system andthe standby system are implemented on a same server apparatus.
 15. Thescaling control method according to claim 14, wherein the serverapparatus comprises: a virtual network function (VNF) implemented bysoftware operating on a virtual machine; and an NFVI (Network FunctionsVirtualization Infrastructure) that provides an execution infrastructurefor the VNF, wherein the NFVI includes at least one of virtualizedcomputing, storage, and network resources obtained by virtualizing, witha virtualization layer, at least one of hardware computing, storage, andnetwork resources.
 16. A scaling control method of an active system of aredundant system executing processing and a standby system of theredundant system being able to perform at least scale-up out of thescale-up and scale-down, the scaling control method comprising:instructing, by a control apparatus, the standby system to performscale-up, when the active system needs to be scaled up; by the standbysystem, responsive to the instruction and in case of performing thescale-up, increasing the number of virtual CPUs (Central ProcessingUnits), allocating one or more processes to one or more virtual CPUsadded, and transmitting a scale-up completion notification to thecontrol apparatus when the scale-up is completed; upon reception of thescale-up completion notification from the standby system that completesthe scale-up, controlling, by the control apparatus, to execute systemswitching to switch the standby system undergoing the scale-up to a newactive system, and to switch the active system before the systemswitching to a new standby system; imposing, by the new standby system,a processing restriction on the new active system, after the systemswitching; instructing, by the control apparatus, the new standby systemto perform scale-up in the same way as the standby system thattransitions to the new active system; and releasing, by the controlapparatus, the processing restriction imposed on the new active system,upon completion of the scale-up of the new standby system.
 17. A scalingcontrol method of an active system of a redundant system executingprocessing and a standby system of the redundant system being able toperform at least scale-down, the scaling control method; comprising:when the active system needs to be scaled down, imposing, by the controlapparatus, a processing restriction on the active system; instructing,by the control apparatus, the standby system to perform scale-down; thestandby system, in performing the scale-down, decreasing the number ofvirtual CPUs (Central Processing Units), releasing allocation of one ormore processes allocated to one or more virtual CPUs deleted, andtransmitting a scale-down completion notification to the controlapparatus when the scale-down is completed; upon reception of thescale-down completion notification from the standby system, controlling,by the control apparatus, to execute system switching of the redundantsystem to switch the standby system undergoing the scale-down to a newactive system and to switch the active system to a new standby system;instructing, by the control apparatus, the new standby system to performscale-down in the same way as the standby system that transitions to thenew active system; and releasing, by the control apparatus, theprocessing restriction on the new active system upon completion of thescale-down of the new active system.
 18. A non-transitorycomputer-readable recording medium storing therein a program causing acomputer to execute a control process of a redundant system constitutedby an active system and a standby system, wherein the active systemexecutes processing and the standby system is able to perform at leastone of scale-up and scale-down, the control process comprising: issuingan instruction to the standby system to perform scale-up or scale-downwhen the scale-up or the scale-down of the active system is needed, thestandby system, responsive to the instruction, in case of performing thescale-up, increasing the number of virtual CPUs (Central ProcessingUnits) included in the standby system and allocating one or moreprocesses to one or more virtual CPUs added, the standby system,responsive to the instructions, in case of performing the scale-down,decreasing the number of virtual CPUs included in the standby system andreleasing allocation of one or more processes allocated to one or morevirtual CPUs deleted, and transmitting a completion notification to thecontrol apparatus when the scale-up or scale-down is completed; andcontrolling, upon reception of the completion notification from thestandby system, to execute system switching of the redundant system toswitch the standby system undergoing the scale-up or scale-down to a newactive system and to switch the active system before the systemswitching to a new standby system.
 19. The non-transitorycomputer-readable recording medium according to claim 18, storing therein a program causing the computer to execute processing comprising:performing scale-up or scale-down of the new standby system in the sameway as the standby system that becomes the new active system aftersystem switching.
 20. A non-transitory computer-readable recordingmedium storing therein a program causing a computer to execute a controlprocess of a redundant system constituted by an active system thatexecutes processing and a standby system that is able to perform atleast scale-up out of scale-up and scale-down, the control processcomprising: instructing, by the control process, the standby system toperform scale-up, when the active system needs to be scaled up; thestandby system, in performing the scale-up, increasing the number ofvirtual CPUs (Central Processing Units), allocating one or moreprocesses to one or more virtual CPUs added, and transmitting a scale-upcompletion notification to the control apparatus when the scale-up iscompleted; upon reception of the scale-up completion notification fromthe standby system undergoing the scale-up, controlling, by the controlprocess, to execute system switching of the redundant system to switchthe standby system that completes the scale-up to a new active systemand to switch the active system before the system switching to a newstandby system; imposing, by the new standby system, a processingrestriction on the new active system; instructing, by the controlprocess, the new standby system to perform scale-up in the same way asthe standby system that becomes the new active system; and releasing, bythe control process, the processing restriction imposed on the newactive system, upon reception of a scale-up completion notification fromthe new standby system.
 21. A non-transitory computer-readable recordingmedium storing therein a program causing the computer to execute acontrol process of scaling down an active system of a redundant systemconstituted by the active system that executes processing and a standbysystem that is able to perform at least scale-down out of scale-up andscale-down: imposing, by the control process, a processing restrictionon the active system before the system switching; instructing, by thecontrol process, the standby system before the system switching toperform scale-down; the standby system, in performing the scale-down,decreasing the number of virtual CPUs (Central Processing Units),releasing allocation of one or more processes allocated to one or morevirtual CPUs deleted, and transmitting a scale-down completionnotification to the control apparatus when the scale-down is completed;upon reception of the scale-down completion notification from thestandby system that completes the scale-down, controlling, by thecontrol process, to execute system switching of the redundant system toswitch the standby system undergoing the scale-down to a new activesystem and to switch the active system before the system switching to anew standby system; instructing, by the control process, the new standbysystem to perform scale-down as the standby system that becomes the newactive system; and releasing, by the control process, the processingrestriction imposed on the new active system, upon completion of thescale-down of the new standby system.